1. Field of the Invention
The present disclosure relates generally to a Metal-Clad Cable Type MC. More particularly, the present disclosure relates to a Metal-Clad Cable Type MC assembly which includes electrical conductors and a non-linear bonding/grounding conductor that engages the metal cladding to provide a desired ground path, while facilitating removal of the cladding during installation.
2. Discussion of Related Art
Armored cable (“AC”) and Metal-Clad (“MC”) cable provide electrical wiring in various types of construction applications. The type, use and composition of these cables must satisfy certain standards as set forth, for example, in the National Electric Code (NEC®). These cables house electrical conductors within a metal armor. The metal armor may be flexible to enable the cable to bend while still protecting the conductors against external damage during and after installation. The armor which houses the electrical conductors may be made from steel or aluminum, copper-alloys, bronze-alloys and/or aluminum alloys. Typically, the metal armor sheath is formed from strip steel, for example, which is helically wrapped to form a series of interlocked “S” shaped sections along a longitudinal length of the cable. Alternatively, the sheaths may be made from smooth or corrugated metal.
MC cable is manufactured according to Underwriters Laboratories Inc. Standard ANSI/UL 1569 and includes a conductor assembly with a plurality of electrical conductors having a particular AWG (American Wire Gauge) size. Metal-Clad Cable with interlocked armor must contain a bare or insulated equipment grounding conductor (EGC) or may contain a bonding/grounding conductor. The electrical conductors and the ground conductor are cabled together in a left or right hand lay and encased collectively in an overall covering. The assembly is then fed into an armoring machine where metal tape is helically applied around the assembly to form a metal sheath. The metallic sheath of continuous or corrugated Type MC Cable may be used as an equipment grounding conductor if the ohmic resistance satisfies the requirements of UL 1569. As noted, a bonding/grounding conductor is often included. This bonding/grounding conductor, in combination with the metallic sheath, shall satisfy UL ohmic resistance requirements. In such cases, the metallic sheath and the bonding/grounding conductor comprise what is referred to as a metallic sheath assembly that is listed and identified as an equipment grounding conductor.
Type MC Cable includes either a covering over all of the electrically insulated conductors and the equipment grounding conductor after cabling, or a covering over just the electrical insulated conductors combined after cabling with the bonding/grounding conductor is positioned externally separate from this overall covering. This covering material is typically a tape of nonmetallic material composed of polypropylene or polyester. This covering material does not provide conductor to conductor mechanical protection nor does it provide protection within an enclosure such as a junction box or panel when the cable is installed therein.
In use, the metallic sheath must be removed from around the electrical conductors in order to make appropriate terminations at junction boxes, panel boards, and the like. Typically this involves cutting the metallic sheath and pulling the cut portion of the sheath along the conductors until the cut portion slides off the ends of the conductors. This can, in practice, be difficult. In order to comply with the DC Resistance of Ground Path and Tightness of Armor Test Requirements, the metallic sheath must be applied so that it is tight on the conductors and the bonding/grounding conductor. This tight packing arrangement results in substantial frictional resistance between the metallic sheath and the conductors and bonding/grounding conductor when attempting to slide the sheath off the cable assembly.
Thus, it would be desirable to provide an improved Type MC Metal Clad Cable that meets applicable DC Resistance of Ground Path and Tightness of Armor Test requirements, but that includes one or more features that make it easier to remove the metal sheathing when making electrical connections in the field.